4-Channel 5V Relay Shield for Arduino
This relay shield plugs directly onto an Arduino Uno header and controls four independent relay channels from GPIO digital pins. Each relay switches up to 250V AC at 10A or 30V DC at 10A, covering mains lighting, heating circuits, and 12V/24V DC loads. Opto-isolators on each control line protect the Arduino from relay coil back-EMF and keep the microcontroller circuit electrically separated from the switched load.
- 4 relay channels — independently controlled from 4 Arduino digital pins
- 250V AC / 10A rating — handles UK mains lighting and small heating loads
- Opto-isolated inputs — protects Arduino from relay coil transients
- NO and NC contacts — normally-open and normally-closed on each channel
- LED indicator per channel — shows relay state without a multimeter
- Fits Arduino Uno headers — direct plug-in, no wiring needed for control
| Specification | Value |
|---|---|
| Channels | 4 |
| Relay rating (AC) | 250V AC, 10A |
| Relay rating (DC) | 30V DC, 10A |
| Control voltage | 5V (from Arduino Uno) |
| Trigger logic | Active low (LOW = relay on) |
| Isolation | Opto-coupler per channel |
Which Arduino pins control the relay channels?
The shield maps channels 1–4 to Arduino digital pins 4, 5, 6, and 7 by default. Set a pin LOW to energise the relay (active-low logic); set it HIGH or leave it floating to de-energise. The active-low design means relays are off when the Arduino is powered but not yet running code — safe for most switching applications.
Can the relay shield switch 230V UK mains?
The relay contacts are rated for 250V AC and handle UK 230V mains. Mains switching requires proper insulated enclosures, appropriately rated cables, and compliance with Part P of the Building Regulations for fixed electrical installations. The relay shield itself is rated for the voltage — safe use depends on how you wire the switched load.
Best for
Arduino home automation, mains light switching, heating and cooling control, garage door automation, pump control, 12V/24V DC motor switching, irrigation valve control, and any project needing up to four independently switched high-voltage or high-current loads.
Why Kunkune
Shipped from UK stock. 60-day returns, no minimum order. Fast Royal Mail delivery.
Buying in bulk? For orders of 10+ units, contact us for trade pricing.
